There is a substantial market for burn therapy and for the repair or support of appropriate epithelial tissues and other wound and skin closure products. For example, venous leg ulcers affect about 1 million people in the United States and 3 million worldwide, and other ulcer conditions such as diabetic ulcers and pressure ulcers (bedsores), affect approximately 10 million people worldwide. Venous ulcer standard care can take over 6 months to heal a wound and cost in excess of $10,000. Furthermore, foot ulcers are a leading cause of hospitalization among diabetics and are estimated to cost the U.S. healthcare system over $1 billion annually. Estimates for hospitalizations for burns in the United States range from 60,000 to 80,000 annually, and costs for recovery from acute injuries range from $36,000 to $117,000 per patient. Human skin equivalent cultures are commonly used in such applications.
Much interest is currently being expressed in the use of stem cells for a variety of tissue replacement therapies. These therapies may be effective for millions of people suffering from diseases ranging from diabetes and sclerosis of the liver to Parkinson's disease and multiple sclerosis.
Mouse 3T3 fibroblast cells are extensively used as feeder layers to enhance the cultivation of human keratinocyte in vitro. Once inactivated to inhibit their proliferation, 3T3 cells are used as a mitotically inactivated “feeder layer” of fibroblasts. Stem cells are also commonly grown on feeder cell layers in vitro. Stem cells depend on cytokines and other factors produced by the feeder cells to prevent differentiation.
However, it is undesirable to have mouse cells remaining in products for use in humans. Such cells can lead to allergic reactions and rejection of transplanted cells. Their presence in a therapeutic product also increases the potential of exposure to xenobiotic pathogens. Thus, robust, sensitive, and accurate methods of detecting contaminating mouse cells in human cell cultures are needed.